Kinetically Controlled Nucleation Enabled by Tunable Microfluidic Mixing for the Synthesis of Dendritic Au@Pt Core/Shell Nanomaterials.

The nucleation stage plays a decisive role in determining nanocrystal morphology and properties; hence, the ability to regulate nucleation is critical for achieving high-level control. Herein, glass microfluidic chips with S-shaped mixing units are designed for the synthesis of Au@Pt core/shell materials. The use of hydrodynamics to tune the nucleation kinetics is explored by varying the number of mixing units. Dendritic Au@Pt core/shell nanomaterials are controllably synthesized and a formation mechanism is proposed. As-synthesized Au@Pt exhibited excellent ethanol oxidation activity under alkaline conditions (8.4 times that of commercial Pt/C). This approach is also successfully applied to the synthesize of Au@Pd core/shell nanomaterials, thus demonstrating its generality.

Sensitive electrochemical measurement of nitric oxide released from living cells based on dealloyed PtBi alloy nanoparticles.

Nitric oxide (NO), as a vital signaling molecule related to different physiological and pathological processes in living systems, is closely associated with cancer and cardiovascular disease. However, the detection of NO in real-time remains a difficulty. Here, PtBi alloy nanoparticles (NPs) were synthesized, dealloyed, and then fabricated to NP-based electrodes for the electrochemical detection of NO. Transmission electron microscopy (TEM), small-angle X-ray scattering (SAXS), and nitrogen physical adsorption/desorption show that dealloyed PtBi alloy nanoparticles (dPtBi NPs) have a porous nanostructure. Electrochemical impedance spectroscopy and cyclic voltammetry results exhibit that the dPtBi NP electrode possesses unique electrocatalytic features such as low charge transfer resistance and large electrochemically active surface area, which lead to its excellent NO electrochemical sensing performance. Owing to the higher density of catalytical active sites formed PtBi bimetallic interface, the dPtBi NP electrode displays superior electrocatalytic activity toward the oxidation of NO with a peak potential at 0.74 V vs. SCE. The dPtBi NP electrode shows a wide dynamic range (0.09-31.5 µM) and a low detection limit of 1 nM (3σ/k) as well as high sensitivity (130 and 36.5 µA µM-1 cm-2). Moreover, the developed dPtBi NP-based electrochemical sensor also exhibited good reproducibility (RSD 5.7%) and repeatability (RSD 3.4%). The electrochemical sensor was successfully used for the sensitive detection of NO produced by live cells. This study indicates a highly effective approach for regulating the composition and nanostructures of metal alloy nanomaterials, which might provide new technical insights for developing high-performance NO-sensitive systems, and have important implications in enabling real-time detection of NO produced by live cells.

Quantitative Analysis of Nanoplastics in Single Cells by Subcellular Chromatography.

The accumulation and spatial distribution of intracellular nanoplastic particles provide useful information about their spatiotemporal toxicological effects mediated by the physicochemical parameters of nanoplastics in living cells. In this study, a sample injection-transfer method was designed with an accuracy of up to femtoliters to attoliters to match the volume required for ultranarrow-bore open-tubular liquid chromatography. The separation and concentration quantification of mixed polystyrenes in different regions in living cells were achieved by directly transferring picoliter/femtoliter volumes of intracellular cytoplasm to an ultranarrow-bore open-tubular chromatographic column. The measurement of pollutant concentration in different areas of a small-volume target (single cell) was realized. This method is expected to be used in the qualitative and quantitative analyses of complex, mixed, and label-free nanoplastics (a few nm in size) in the subregions of living cells.

Dealloying of Pt1Bi2 intermetallic toward optimization of electrocatalysis on a Bi-continuous nanoporous core-shell structure.

Noble metal nanoporous materials hold great potential in the field of catalysis, owing to their high open structures and numerous low coordination surface sites. However, the formation of porous nanoparticles is restricted by particle size. Herein, we utilized a Pt1Bi2 intermetallic nanocatalyst to develop a dealloying approach for preparing nanoparticles with a bi-continuous porous and core-shell structure and proposed a mechanism for the formation of pores. The particle size used to form the porous structure can be <10 nm, which enhances the nanocatalyst's performance for the oxygen reduction reaction (ORR). This study provides a new understanding of the formation of porous materials via a dealloying approach.

Spontaneous Phase Segregation Enabling Clogging Aversion in Continuous Flow Microfluidic Synthesis of Nanocrystals Supported on Reduced Graphene Oxide.

Eliminating clogging in capillary tube reactors is critical but challenging for enabling continuous-flow microfluidic synthesis of nanoparticles. Creating immiscible segments in a microfluidic flow is a promising approach to maintaining a continuous flow in the microfluidic channel because the segments with low surface energy do not adsorb onto the internal wall of the microchannel. Herein we report the spontaneous self-agglomeration of reduced graphene oxide (rGO) nanosheets in polyol flow, which arises because the reduction of graphene oxide (GO) nanosheets by hot polyol changes the nanosheets from hydrophilic to hydrophobic. The agglomerated rGO nanosheets form immiscible solid segments in the polyol flow, realizing the liquid-solid segmented flow to enable clogging aversion in continuous-flow microfluidic synthesis. Simultaneous reduction of precursor species in hot polyol deposits nanocrystals uniformly dispersed on the rGO nanosheets even without surfactant. Cuprous oxide (Cu2O) nanocubes of varying edge lengths and ultrafine metal nanoparticles of platinum (Pt) and palladium (Pd) dispersed on rGO nanosheets have been continuously synthesized using the liquid-solid segmented flow microfluidic method, shedding light on the promise of microfluidic reactors in synthesizing functional nanomaterials.

Plasma-Assisted Fabrication of Molecularly Imprinted NiAl-LDH Layer on Ni Nanorod Arrays for Glyphosate Detection.

An inorganic-framework molecularly imprinted NiAl layered double hydroxide (MI-NiAl-LDH) with specific template molecule (glyphosate pesticide, Glyp) recognition ability was prepared on Ni nanorod arrays (Ni NRAs) through electrodeposition followed by a low-temperature O2 plasma treatment. The freestanding Ni/MI-NiAl-LDH NRA electrode had highly enhanced sensitivity and selectivity. The electrocatalytic oxidation of Glyp was proposed to occur at Ni3+ centers in MI-NiAl-LDH, and the current response depended linearly on the Glyp concentration from 10.0 nmol/L to 1.0 µmol/L (R2 = 0.9906), with the limit of detection (LOD) being 3.1 nmol/L (S/N = 3). An exceptional discriminating capability with tolerance for other similar organophosphorus compounds was achieved. Molecular imprinting (N and P residues) affected the electronic structure of NiAl-LDH, triggering the formation of highly active NiOOH sites at relatively lower anodic potentials and substantially enhancing the electrocatalytic oxidation ability of the NiAl-LDH interface toward the C-N bonds in Glyp. In combination with the surface enrichment effect of MI-NiAl-LDH toward template molecules, the electrochemical oxidation signal intensity of Glyp increased significantly, with a greater peak separation from interfering molecules. These results challenge the common belief that the excellent performance of inorganic-framework molecularly imprinted interfaces arises from their specific adsorption of template molecules, providing new insight into the development of high-performance organic-pollutant-sensing electrodes.

Evaluation of the effect of nitrate and chloride on Cd(II)-induced cell oxidative stress by scanning electrochemical microscopy.

Cadmium (Cd) is one of the most prevalent toxic metal pollutants, which is widely distributed in various environmental media and organisms. Literature studies have documented that Cd could stimulate cellular oxidative stress, and the increased intracellular reactive oxygen species (ROS) might destroy certain proteins and DNA and subsequently lead to cell apoptosis. Although several studies have studied the co-exposure between cadmium and other metals, information on the potential effects of Cd and its counterions is still lacking. In the present study, we explored the effects of nitrate and chloride on oxidative stress induced by Cd(II) at environmental exposure levels in human breast cancer cells (MCF-7) using scanning electrochemical microscopy (SECM). After incubation in CdCl2 or Cd(NO3)2, ROS production is concentration-dependent and time-dependent, and the variation trend is consistent. When MCF-7 cells were incubated at a constant Cd2+ concentration, it was found that the higher the concentration ratio of Cd(NO3)2/CdCl2, the less ROS was generated. Combined with cell-viability, intracellular acidification as well as antioxidants system tests, we observed that nitrate could be reduced to nitrite and then inhibit Cd-induced oxidative stress. Benefitting from real-time in situ imaging of cells by SECM, H2O2 was detected and quantified in a noninvasive way, and the effect of Cd at environmental exposure levels on cellular oxidative stress was explored deeper and more comprehensively. Prospectively, cytotoxicological methods based on the SECM technique would be established to explore toxic pollutant co-exposure issues at environmental exposure levels.

Analytical methods for obtaining binding parameters of drug-protein interactions: A review.

The study of drug-protein interactions can reveal the corresponding binding mechanisms, providing valuable information for the early phase drug development and development of new drugs. This article reviews the methods used for obtaining the binding parameters of drug-protein systems. The methods include equilibrium dialysis, high-performance affinity chromatography, capillary electrophoresis, spectroscopy, calorimetry, competition and displacement, mass spectrometry, fluorescence resonance energy transfer, and thermal stability shift analysis. Relevant parameters include the association constant, number of binding sites, thermodynamic properties, binding force types, binding site types, binding distances, changes in protein conformation, and changes in protein stability. In addition, the review also summarizes the principles, advantages, and limitations of each method in detail. The comparison of parameter information can not only guide method selection but also provide valuable reference information for in-depth exploration of drug-protein interaction mechanisms.

Displacement Reaction-Assisted Synthesis of Sub-Nanometer Pt/Bi Boost Methanol-Tolerant Fuel Cells.

The development of new synthetic methods for methanol-tolerant catalysts with improved performance is of fundamental importance for the commercialization of fuel cells. Herein, we reported a facile displacement reaction-assisted synthesis of graphene-supported sub-nanometer Pt/Bi catalysts (Pt/Bi/rGO). Bismuth (0) nanoparticles produced by NH3BH3 reduction can be further dissolved into the ethylene glycol, implying Bi(0) has a strong interaction with the hydroxyl group. That is the key interaction between Bi(0) and the functional group on the rGO to form the ultra-small Bi/rGO catalyst. Furthermore, Pt clusters are obtained by the displacement between Bi(0) and HPtCl4 and are directly anchored to the rGO surface. The as-synthesized Pt/Bi/rGO catalyst exhibits high oxygen reduction mass activity and high tolerance to methanol poisoning. In the presence of 0.5 mol/L CH3OH, the initial potential and activity of ORR were almost unchanged, which demonstrated great potential in the application of direct methanol fuel cells.

Determination of Nanoplastics Using a Novel Contactless Conductivity Detector with Controllable Geometric Parameters.

Plastic waste in the environment is continuously degraded to form nanoplastic particles, and its harm has attracted widespread attention. At present, the identification and quantification of nanoplastics are performed by visual observation and using some spectroscopy methods, which are time-consuming and lack accuracy. Therefore, this study proposes a contactless conductivity detector (C4D) based on a glass microfluidic chip with controllable geometric parameters to quantify nanoplastics. We found that when the insulating layer thickness was 15 µm, the electrode spacing was 1 mm, and the shielding method was on-chip shielding, the detector displayed the best performance. The detector possesses a simple structure with high sensitivity and outstanding reproducibility, that is, the limit of detection of KCl solutions can reach the micromolar level, and the intraday RSD is 0.2% (n = 5). This work uses a microfluidic chip C4D to study nanoplastics for the first time, and the limit of detection is 0.25 µg/mL and the quantitative limit is 0.8 µg/mL. In addition, plant experiments have verified that terrestrial plants can absorb nanoplastics in water, expanding the application of contactless conductivity detectors and providing a new method for the quantitative analysis of nanoplastics.

Extension of hydrodynamic chromatography to DNA fragment sizing and quantitation.

Hydrodynamic chromatography (HDC) is a technique originally developed for separating particles. We have recently extended it to DNA fragment sizing and quantitation. In this review, we focus on this extension. After we briefly introduce the history of HDC, we present the evolution of open tubular HDC for DNA fragment sizing. We cover both the theoretical aspect and the experimental implementation of this technique. We describe various approaches to execute the separation, discuss its representative applications and provide a future perspective of this technique in the conclusion section of this review.

Visually precise, low-damage, single-cell spatial manipulation with single-pixel resolution.

The analysis of single living cells, including intracellular delivery and extraction, is essential for monitoring their dynamic biochemical processes and exploring intracellular heterogeneity. However, owing to the 2D view in bright-field microscopy and optical distortions caused by the cell shape and the variation in the refractive index both inside and around the cells, achieving spatially undistorted imaging for high-precision manipulation within a cell is challenging. Here, an accurate and visual system is developed for single-cell spatial manipulation by correcting the aberration for simultaneous bright-field triple-view imaging. Stereo information from the triple view enables higher spatial resolution that facilitates the precise manipulation of single cells. In the bright field, we resolved the spatial locations of subcellular structures of a single cell suspended in a medium and measured the random spatial rotation angle of the cell with a precision of ±5°. Furthermore, we demonstrated the visual manipulation of a probe to an arbitrary spatial point of a cell with an accuracy of <1 pixel. This novel system is more accurate and less destructive for subcellular content extraction and drug delivery.

A scalable synthesis of ternary nanocatalysts for a high-efficiency electrooxidation catalysis by microfluidics.

Microfluidic synthesis has attracted extensive attention due to the ability for the multistep precise control of the synthesis parameters, continuous and reproducible preparation, and its ease of integration. However, its commercial application is still affected by its low production efficiency. In this case, we report a high-throughput continuous flow synthesis of highly dispersed PtFeCu/C nanocatalysts using a metal microchip setup with four parallel channels. The high flow rate and integrated channels enabled improving the throughput, whereby 1.33 g h-1 of catalysts could be achieved with the flow rate of 1200 mL h-1 under the experimental conditions. The as-prepared PtFeCu/C exhibited excellent performance, 1.94 times higher than Pt/C for methanol oxidation. More importantly, the yield of the PtFeCu/C nanocatalysts could be further increased through designing numerous parallel channels, which might provide a promising approach for large-scale commercialization of the catalysts. Such a high-throughput fabrication pathway is significant for the large-scale industrial production of nanomaterials.

Visual and real-time imaging focusing for highly sensitive laser-induced fluorescence detection at yoctomole levels in nanocapillaries.

A highly sensitive laser-induced fluorescence detection system with real-time imaging focusing instead of the use of fluorescent reagents were developed for the detection of analytes in nanocapillaries. A cylindrical lens was adopted for the shaping of a laser beam to increase its spatial resolution. The limit of detection with a capillary having a radius of 440 nm was 6.76 yoctomoles (or four molecules) for fluorescein, and 84.5 yoctomoles (or 51 molecules) for FAM-labeled Hsa-miR-17. The designed system exhibited high sensitivity and stability for femtoliters of sample and was hence indicated to be suitable for analyses of single cells.

[Application of porous layer open tubular capillary columns with narrow inner diameter in nanoflow-high performance liquid chromatography for N-derivatized amino acid enantiomers].

Porous layer open tubular capillary columns with a narrow inner diameter (NPLOT) have potential in life science, especially in single-cell analysis. In this work, quinidine-based chiral NPLOT columns were prepared by in-situ thermal-initiated polymerization. The porous layer of the organic polymer was prepared with a 6 µm i. d capillary by in-situ thermal-initiated polymerization, following which the thickness and morphology of the NPLOT column were observed for different durations (3 h, 6 h, and 9 h) of polymerization. The thicknesses of the porous layer were 103±51 nm and 210±51 nm when polymerization was conducted for 3 h and 6 h, respectively. Subsequently, the columns prepared under 3 h of polymerization were applied in nanoflow-high performance liquid chromatography for the enantioseparation of N-derivatized amino acid enantiomers. Baseline separation was achieved in 2 min. The sample volume consumed was of the picoliter level, which would provide a means of research for single-cell analysis.

A carbon-supported BiSn nanoparticles based novel sensor for sensitive electrochemical determination of Cd (II) ions.

A novel sensor based on carbon supported BiSn alloy nanoparticles (BiSn@C) was prepared for the sensitive detection of Cd2+. The BiSn@C and Nafion modified glassy carbon electrode (GCE) exhibited improved electrochemical performance in Cd2+ detection, because of its large specific surface area, abundance of active sites, good electrical conductivity, and strong cation exchange ability. Under the optimum conditions, the fabricated sensor showed good linearity of its response from 0.01 µmol/L to 30 µmol/L for the detection of Cd2+ and a limit of detection (LOD) of 3 nmol/L, which is considerably lower than the limit specified for safe drinking water as guided by the World Health Organization. The Nafion/BiSn@C/GCE was successfully applied for determination for trace Cd2+ in river samples with satisfying recoveries using the standard addition method.

In-tube solid-phase microextraction capillary column packed with mesoporous TiO2 nanoparticles for phosphopeptide analysis.

In this study, an in-tube solid-phase microextraction column packed with mesoporous TiO2 nanoparticles, coupled with MALDI-TOF-MS, was applied to the selective enrichment and detection of phosphopeptides in complex biological samples. The mesoporous TiO2 nanoparticles with high specific surface areas, prepared by a sol-gel and solvothermal method, were injected into the capillary using a slurry packing method with in situ polymerized monolithic segments as frits. Compared with the traditional solid-phase extraction method, the TiO2 -packed column with an effective length of 1 cm exhibited excellent selectivity (α-casein/ß-casein/BSA molar ratio of 1:1:100) and sensitivity (10 fmol of a ß-casein enzymatic hydrolysis sample) for the enrichment of phosphopeptides. These performance characteristics make this system suitable for the detection of phosphorylated peptides in practical biosamples, such as nonfat milk.

Three-electron reversible redox for a high-energy fluorophosphate cathode: Na3V2O2(PO4)2F.

A three-electron structural reaction for Na3V2O2(PO4)2F (Na3VOPF) in space group I4/mmm shows a priori stabilisation in terms of long-life in the voltage range of 2.0-4.5 V, with embedding of more than one sodium ion to generate Na5VOPF upon discharge to 1.0 V in the first cycle, thereby increasing the specific capacity from ∼170 mA h g-1. The capacity of the crystals was 180 mA h g-1 after 20 cycles. The results provide a probable route to improve fluorophosphate cathode performance.

Enabling Colloidal Synthesis of Edge-Oriented MoS2 with Expanded Interlayer Spacing for Enhanced HER Catalysis.

By selectively promoting heterogeneous nucleation/growth of MoS2 on graphene monolayer sheets, edge-oriented (EO) MoS2 nanosheets with expanded interlayer spacing (∼9.4 Å) supported on reduced graphene oxide (rGO) sheets were successfully synthesized through colloidal chemistry, showing the promise in low-cost and large-scale production. The number and edge length of MoS2 nanosheets per area of graphene sheets were tuned by controlling the reaction time in the microwave-assisted solvothermal reduction of ammonium tetrathiomolybdate [(NH4)2MoS4] in dimethylformamide. The edge-oriented and interlayer-expanded (EO&IE) MoS2/rGO exhibited significantly improved catalytic activity toward hydrogen evolution reaction (HER) in terms of larger current density, lower Tafel slope, and lower charge transfer resistance compared to the corresponding interlayer-expanded MoS2 sheets without edge-oriented geometry, highlighting the importance of synergistic effect between edge-oriented geometry and interlayer expansion on determining HER activity of MoS2 nanosheets. Quantitative analysis clearly shows the linear dependence of current density on the edge length of MoS2 nanosheets.

Quantitatively in Situ Imaging Silver Nanowire Hollowing Kinetics.

We report the in situ investigation of the morphological evolution of silver nanowires to hollow silver oxide nanotubes using transmission X-ray microscopy (TXM). Complex silver diffusion kinetics and hollowing process via the Kirkendall effect have been captured in real time. Further quantitative X-ray absorption analysis reveals the difference between the longitudinal and radial diffusions. The diffusion coefficient of silver in its oxide nanoshell is, for the first time, calculated to be 1.2 × 10-13 cm2/s from the geometrical parameters extracted from the TXM images.